There is provided a process for ring opening of aromatics and cycloaliphatics, as well as isomerization of aliphatics. The feedstream to this process comprises C.sub.6 cycloparaffins and/or benzene. The process involves the use of at least two reactors connected in series. The first reactor comprises a zeolite catalyst and is operated under conditions which particularly promote ring opening. A downstream reactor is operated under conditions to promote isomerization of aliphatics.
A unit process which is frequently encountered in petroleum refining is paraffin isomerization. Paraffin isomerization of linear (straight chain) paraffins produces branched chain paraffins. In such a process, as conventionally operated, low molecular weight C.sub.4-C.sub.6 paraffins are converted to iso-paraffins in the presence of an acidic catalyst such as aluminum chloride. Recently, C.sub.6 +, preferably C.sub.10 + n-paraffins, have been isomerized, in the presence of large pore size zeolites to produce branched chain paraffins by skeletal rearrangement. The latter process can find application in dewaxing.
Isomerization is one of several reactions which occur in reforming of naphthas. Reforming of naphthas is undertaken to upgrade a low octane naphtha to a higher octane effluent. One of the octane enhancing reactions which occurs during reforming is the isomerization of n-paraffins to isoparaffins. Under the process conditions of reforming, other reactions which occur are aromatization (or dehydrocyclization), and dehydrogenation, with some cracking.
Paraffin isomerization catalysts may also be employed as ring opening catalysts for removal of aromatics and aromatic precursors from reformer feedstocks. For example, cyclohexane, a precursor to benzene, may be rearranged over commercial paraffin isomerization catalysts to a mixture of branched paraffins. Branched paraffins are only partly aromatized in reforming whereas cyclohexane is almost completely converted to benzene. Application of paraffin isomerization catalysts for ring opening aromatics and aromatic precursors will no doubt become more important as environmental regulations limiting aromatics in gasoline become more stringent.